Given two catalogs K and K' of n and n' astrophysical sources, respectively, Aspects (Association positionnelle/probabiliste de catalogues de sources) computes, for any objects Mi ∈ K and M'j ∈ K', the probability that M'j is a counterpart of Mi, i.e. that they are the same source. To determine this probability of association, the code takes into account the coordinates and the positional uncertainties of all the objects. Aspects also computes the probability P(Ai, 0 | C ∩ C') that Mi has no counterpart.
Aspects is written in Fortran 95 and requires a number of Numerical Recipes routines in Fortran 90.